Should the US Covid Mortality Rate Be Lowered?

Since April I’ve been estimating that the covid mortality rate in the US is around 0.6 percent. That number is based on the few systemic random surveys of immunity that have been conducted in this country and elsewhere. Lately I’ve been wondering whether I should revise that estimate downward.

About a month ago the CDC released a study estimating a US mortality rate of 0.3 percent. I questioned that estimate at the time, and the second wave of the CDC’s serology meta-analysis reinforced my skepticism. Still, there are plausible reasons why the mortality rate may have decreased since the early days of the epidemic. Medical care has improved with experience. As I noted in my last post, nursing homes, the source of more than 40 percent of corona deaths, have tightened their safety measures. On the other hand, there isn’t compelling evidence to support the contention that the virus is now infecting relatively younger people who are less likely to die from the infection.

Now here comes a new random serology survey out of Riverside California. Some observations:

Of about 3,500 people contacted, 1,726 people were tested, and 101 tested positive, which is a positivity rate of 5.9 percent. [Principal investigator Dr. Cameron] Kaiser says that means somewhere between 118,000 and 175,000 people have already had the virus, which might give us a better idea of the true fatality rate. “We haven’t finished the data analysis, but I will say most estimates place it somewhere between 0.5 and 1 percent overall, and I’m not seeing anything with our numbers that challenges that,” he said.

So I’m sticking with the 0.6 percent estimate for now.


24-Hour Party Retirees?

Supposedly the current surge in hotspots across the South and Southwest is being driven by young people, who in turn spread their contagion outward and upward to their elders. This narrative could be confirmed with data: a younger average age of infection leads to younger hospitalized cases, in turn leading to relatively younger people dying of the disease. But the data are hard to come by.

The CDC used to sort covid case counts and hospitalizations into age categories, but not anymore. Though the daily death count summaries are delayed by two weeks, the CDC does still does categorize deaths demographically. The current surge in cases and percent-positives began in mid-June; death counts, a lagging indicator of infection, began their corresponding jump on July 7.  Provisional CDC counts show that, during the week ending July 11, 78 percent of US deaths occurred among those aged 65 and older — a percentage that’s remained stable since the early days of the epidemic. If younger people are disproportionately testing positive during the recent rise in case counts, then that downward age trend might be an artifact of increased testing among people returning to work and proactively getting themselves tested, rather than a shift in the demographics of contagion.

Though the under-65 death count remains steady, there has been a downward shift within the 65+ demographic. In the July 4-11 provisional stats, the proportion of deaths for those aged 85 and older decreased, while for those aged 75-84 the death rate went up.

The recent decrease in deaths in the oldest demographic stratum might be just a temporary statistical variability that will regress to the mean over the next week or two. Alternatively, it may well reflect tighter safety precautions being exercised at nursing homes. While those 85 and older make up only 2% of the American population, they comprise nearly half of nursing home residents. And nursing homes have accounted for more than 40% of covid deaths in the US. The Kaiser Family Foundation compiled data on case counts from 35 states during the two weeks ending July 8. While new covid cases went up 42 percent overall, new cases originating in nursing homes and other residential facilities increased only 11 percent.

But, while coronavirus deaths among those 85 and older went down, the death toll rose for those aged 75 to 84. Again, random statistical variance might explain it. Alternatively, the jump could be a direct result of societal reopening. Older people living in the community might not be going to the workplace or the bars or the beach, but they do socialize, go shopping, get their hair done, play Mahjong, go out to eat. They could just as easily be catching covid from one another as from the 24-hour party kids. Older people might be experiencing more intense social distancing fatigue, not wanting to waste their few remaining active years locked away in self-isolation.